The present invention relates to a catalyst activator. More particularly the present invention relates to dispersed ionic catalyst activators particularly adapted for use in a solution polymerization process for polymerization of .alpha.-olefins. Such an activator is particularly advantageous for use in a continuous solution polymerization process wherein catalyst, catalyst activator, and at least one polymerizable monomer are continuously added to a reactor operating under solution polymerization conditions, and polymerized product is continuously removed therefrom.
It is previously known in the art to activate Ziegler-Natta polymerization catalysts, particularly such catalysts comprising Group 4 metal complexes containing delocalized .pi.-bonded ligand groups by the use of Bronsted acid salts capable of transferring a proton to form a cationic derivative of such Group 4 metal complexes. Preferred Bronsted acid salts are such compounds containing a noncoordinating anion that are capable of stabilizing the resulting Group 4 metal cation, especially tetrakis(pentafluorophenyl)borate. Examples of such Bronsted acid salt activators, which are a species of ionic activator, are protonated ammonium, sulfonium, or phosphonium salts disclosed in U.S. Pat. No. 5,198,401, U.S. Pat. No. 5,132,380 and EP-A-277,004.
Suitable noncoordinating anions include sterically shielded, bulky anions, especially fluorinated polyarylboron anions such as tetrakis(pentafluorophenyl)borate and diboron anions corresponding to the formula: ##STR1## wherein: S is alkyl, fluoroalkyl, aryl, or fluoroaryl (and where two S groups are present additionally hydrogen),
Ar.sup.F is fluoroaryl, and PA1 X.sup.1 is either hydrogen or halide. PA1 Such diboron anions are disclosed in U.S. Pat. No. 5,447,895. PA1 Additional ionic activators include carbenium, silylium and nonprotonated sulfonium, oxonium or phosphonium salts as well as oxidizing salts such as ferrocenium salts or silver salts. Such additional examples of ionic activating cocatalysts are disclosed in U.S. Pat. No. 5,189,192, U.S. Pat. No. 5,350,723, U.S. Pat. No. 5,387,568 and U.S. Ser. No. 08/304,314, filed Sep. 12, 1994 now U.S. Pat. No. 5,625,087. The teachings of all of the foregoing patents and patent applications are hereby incorporated by reference. PA1 .rho..sub.s is the apparent density of the solid in g/cm.sup.3, PA1 .rho. is the true density of the suspending medium in g/cm.sup.3, both .rho..sub.s and .rho. being measured at 25.degree. C., PA1 g is the gravitational constant (980.665 cm/sec.sup.2), PA1 d.sub.p is the particles diameter in cm, and PA1 .mu..sub.s is the viscosity of the mixture of particles and suspending medium in g/cm/sec. PA1 .mu. is the suspending medium's viscosity in g/cm/sec, and PA1 X is the medium's volume fraction (for example 0.99 for a 1 volume percent suspension). PA1 Ar* is an aryl group, especially 2,6-diisopropylphenyl, 2,6-dimethylphenyl, 2,6-di-t-butylphenyl, or 2,6-diphenylphenyl; and PA1 T independently each occurrence is selected from the group consisting of hydrogen, C.sub.1-4 alkyl or phenyl, or two T groups together with the two carbon moieties form a fused ring system, especially a 1,8-naphthanediyl group. PA1 R.sup.3 in each occurrence independently is selected from the group consisting of hydrogen, hydrocarbyl, hydrocarbyloxy, silyl, germyl, cyano, halo and combinations thereof, (especially, hydrocarbyloxysilyl, halocarbyl, and halohydrocarbyl) said R.sup.3 having up to 20 non-hydrogen atoms, or adjacent R.sup.3 groups together form a divalent derivative (that is, a hydrocarbadiyl, siladiyl or germadiyl group) thereby forming a fused ring system, and PA1 X" independently each occurrence is an anionic ligand group of up to 40 non-hydrogen atoms, or two X" groups together form a divalent anionic ligand group of up to 40 non-hydrogen atoms or together are a conjugated diene having from 4 to 30 non-hydrogen atoms forming a .pi.-complex with M, whereupon M is in the +2 formal oxidation state, and PA1 R*, E and x are as previously defined. PA1 R.sup.3 in each occurrence independently is selected from the group consisting of hydrogen, hydrocarbyl, silyl, germyl, cyano, halo and combinations thereof, said R.sup.3 having up to 20 non-hydrogen atoms, or adjacent R.sup.3 groups together form a divalent derivative (that is, a hydrocarbadiyl, siladiyl or germadiyl group) thereby forming a fused ring system, PA1 each X" is a hydride, hydrocarbyl, hydrocarbyloxy or silyl group, said group having up to 20 non-hydrogen atoms, or two X" groups together form a neutral C.sub.5-30 conjugated diene or a divalent derivative thereof; PA1 Y is --O--, --S--, --NR*--, --PR*--; and PA1 Z is SiR*.sub.2, CR*.sub.2, SiR*.sub.2 SiR*.sub.2, CR*.sub.2 CR*.sub.2, CR*.dbd.CR*, CR*.sub.2 SiR*.sub.2, or GeR*.sub.2, wherein R* is as previously defined. PA1 R.sup.3 each occurrence is independently selected from the group consisting of hydrogen, hydrocarbyl, silyl, germyl, cyano, halo and combinations thereof, said R.sup.3 having up to 20 non-hydrogen atoms, or adjacent R.sup.3 groups together form a divalent derivative (that is a hydrocarbadiyl, siladiyl or germadiyl group) thereby forming a fused ring system; PA1 each X" is a hydrocarbyl, hydrocarbyloxy or silyl group, said group having up to 20 non-hydrogen atoms; PA1 Y' is --OR*, --SR*, --NR*.sub.2, --PR*.sub.2 ; PA1 Z is SiR*.sub.2, CR*.sub.2, SiR*.sub.2 SiR*.sub.2, CR*.sub.2 CR*.sub.2, CR*.dbd.CR*, CR*.sub.2 SiR*.sub.2, or GeR*.sub.2, wherein R* is as previously defined; and PA1 n is a number from 0 to 3. PA1 L* is a neutral Lewis base; PA1 (L*-H).sup.+ is a Bronsted acid; PA1 A.sup.d- is a noncoordinating, compatible anion having charge d-, and PA1 d is an integer from 1 to 3. PA1 More preferably A.sup.d- corresponds to the formula: M'.sup.k+ Q.sub.n' !.sup.d-, wherein: PA1 k is an integer from 1 to 3; PA1 n' is an integer from 2 to 6; PA1 n'-k=d; PA1 M' is an element selected from Group 13 of the Periodic Table of the Elements; and PA1 L* is a nitrogen, sulfur or phosphorus containing Lewis base; PA1 B is boron in an oxidation state of 3; and PA1 Q' is a fluorinated C.sub.1-20 hydrocarbyl group. PA1 Ox.sup.e+ is a cationic oxidizing agent having a charge of e+; PA1 e is an integer from 1 to 3; and PA1 A.sup.d-, and d are as previously defined. PA1 .COPYRGT..sup.+ is a Lewis acid cation containing up to 20 carbon or silicon atoms; and PA1 A.sup.- is as previously defined.
Due to the fact that such activators are fully ionized and the corresponding anion is highly noncoordinating, such activators are extremely effective as olefin polymerization catalyst activators. Disadvantageously, however, because they are ionic salts, such activators are extremely insoluble in aliphatic hydrocarbons and only sparingly soluble in aromatic solvents. It is desirable to conduct most solution polymerizations of .alpha.-olefins in aliphatic hydrocarbon solvents due to the compatibility of such solvents with the monomer and in order to reduce the aromatic hydrocarbon content of the resulting polymer product. Normally, ionic salt activators need to be added to such polymerizations in the form of a solution in an aromatic solvent such as toluene. The use of even a small quantity of such an aromatic solvent for this purpose is undesirable. In addition, for polymerizations such as the preparation of syndiotactic polystyrene using an aromatic solvent such as toluene, the foregoing ionic cocatalysts often are difficult to use in commercial practice due to formation of an oily intractable material.
Accordingly, it would be desirable if there were provided an ionic catalyst activator that could be employed in solution polymerizations that use an aliphatic solvent, including condensed .alpha.-olefin monomer, as well as an aromatic solvent. In addition it would be desirable to provide a new form of ionic catalyst activator that is particularly adapted for use in a continuous solution polymerization reaction where controlled, metered addition of specific quantities of such activator is required.